The present invention relates generally to novel integrated circuit packages that include a new family of miniature antennas in the package.
There is a trend in the semiconductor industry towards the so-called System on Chip (SoC) and System on Package (SoP) concepts. The full integration of systems or subsystems into a single chip, package or module provides many advantages in terms of cost, size, weight, consumption, performance and product design complexity. Several electronic components for consumer applications, such as handsets, wireless devices, personal digital assistants (PDAs) or personal computers (PCs) are becoming more and more integrated into SoP/SoC products.
The concept of integrating a miniature antenna into a package or module is especially attractive owing to the tremendous growth and success of cellular and wireless systems. In particular, there is a new generation of short/medium range wireless applications such as Bluetooth™, Hyperlan, IEEE802.11 and ultra wide band (UWB), Wimax and Zig Bee systems where the progressive system integration into a single, compact product is becoming a key success factor (see for instance, S. Harris and H. Johnston, “Handset Industry Debate Bluetooth™ Chip Options”, WirelessEurope, May 2002).
This concept of integrating a miniature antenna into a package or module is especially attractive as well in GSM, UMTS, PCS 1900, KPCS, CDMA, WCDMA, and GPS.
There have been reported several attempts to integrate an antenna in a package or module. These designs feature two important limitations: first the operating frequency must be large enough to allow a conventional antenna to fit inside the chip; second the antenna performance is poor in terms of gain, mainly due to the losses in the semiconductor material. According to D. Singh, et al., the smallest frequency in which an antenna has been integrated together with an electronic system inside the same was 5.98 GHz. Typical gains that have been achieved with such designs are around −10 dBi.
In general, there is a trade-off between antenna performance and miniaturization. The fundamental limits on small antennas were theoretically established by H. Wheeler and L. J. Chu in the middle 1940's. They stated that a small antenna has a high quality factor (Q), because of the large reactive energy stored in the antenna vicinity compared to the radiated power. Such a high quality factor yields a narrow bandwidth; in fact, the fundamental derived in such theory imposes a maximum bandwidth given a specific size of a small antenna. Related to this phenomenon, it is also known that a small antenna features a large input reactance (either capacitive or inductive) that usually has to be compensated with an external matching/loading circuit or structure. It also means that it is difficult to pack a resonant antenna into a space which is small in terms of the wavelength at resonance. Other characteristics of a small antenna are its small radiating resistance and its low efficiency (see, R. C. Hansen, Fundamental Limitations on Antennas, Proc. IEEE, vol. 69, no. 2, February 1981).
Some antenna miniaturization techniques rely basically on the antenna geometry to achieve a substantial resonant frequency reduction while keeping efficient radiation. For instance, patent application WO 01/54225 A1 discloses a set of space-filling antenna geometries (SFC) that are suitable for this purpose. Another advantage of such SFC geometries is that in some cases they feature a multiband response.
The dimension (D) is a commonly used parameter to mathematically describe the complexity of some convoluted curves. There exist many different mathematical definitions of dimension but in the present document the box-counting dimension (which is well-known to those skilled in advanced mathematics theory) is used to characterize some embodiments (see discussion on the mathematical concept of dimension in W. E. Caswell and J. A. Yorke, “Invisible Errors in Dimension Calculations: Geometric and Systematic Effects”, Dimensions and Entropies in Chaotic Systems, G. Mayer-Kress, editor, Springer-Verlag, Berlin 1989, second edition, pp. 123-136 or K. Judd, A. I. Mees, “Estimating Dimensions with Confidence”, International Journal of Bifurcation and Chaos, 1,2 (1991) 467-470).
So-called chip-antennas are described in H. Tanidokoro, N. Konishi, E. Hirose, Y. Shinohara, H. Arai, N. Goto, “1-Wavelength Loop Type Dielectric Chip Antennas”, Antennas and Propagation Society International Symposium, 1998, IEEE, vol. 4, 1998 (“Tanidokoro, et al.”) or H. Matsushima, E. Hirose, Y. Shinohara, H. Arai, N. Golo, “Electromagnetically Coupled Dielectric Chip Antenna”, Antennas and Propagation Society International Symposium, IEEE, vol. 4, 1998. Those are typically single component antenna products that integrate only the antenna inside a surface-mount device. To achieve the necessary wavelength compression, those antennas are mainly constructed using high permitivity materials such as ceramics. The drawbacks of using such high permitivity materials are that the antenna has a very narrow bandwidth, the material introduces significant losses, and the manufacturing procedure and materials are not compatible with most package manufacturing techniques; therefore they do not currently include other components or electronics besides the antenna, and they are not suitable for a FWSoC or FWSoP.
There have been recently disclosed some RF SoP configurations that also include antennas on the package. Again, most of these designs rely on a conventional microstrip, shorted patch or PIFA antenna that is suitable for large frequencies (and therefore small wavelengths) and feature a reduced gain. In K. Lim, S. Pinel, M. Davis, A. Sutono, C. Lee, D. Heo, A. Obatoynbo, J. Laskar, E. Tantzeris, R. Tummala, “RF-System-On-Package (SOP) for Wireless Communications”, IEEE Microwave Magazine, vol. 3, no. 1, March 2002 (“Lim, et al.”), a SoP including an RF front-end with an integrated antenna is described. The antenna comprises a microstrip patch backed by a cavity which is made with shorting pins and operates at 5.8 GHz. As mentioned in Lim, et al., it is difficult to extend those designs in the 1-6 GHz frequency range where most current wireless and cellular services are located, mainly due to the size of conventional antennas at such large wavelengths. Another design for an antenna on a package is disclosed in Y. P. Zhang, W. B. Li, “Integration of a Planar Inverted F Antenna on a Cavity-Down Ceramic Ball Grid Array Package”, IEEE Symp. on Antennas and Propagation, June 2002. Although the antenna operates at the Bluetooth™ band (2.4 GHz), the IC package is substantially large (15×15 mm) and the antenna performance is poor (gain is below −9 dBi).
Patent application EP 1126522 describes a particular double S-shaped antenna design that is mounted on a BGA package. Although no precise data is given on the package size in the application, typically, S-shaped slot antennas resonate at a wavelength on the order of twice the unfolded length of the S-shaped pattern. Again, this makes the whole package too large for typical wireless applications where the wavelength is above 120 mm. Also, this design requires a combination with high permitivity materials that, in turn, reduce the antenna bandwidth, increase its cost and decreases the overall antenna efficiency.
Regarding the package construction and architecture, there are several standard configurations depending mainly on the application. Some basic architectures are: single-in-line (SIL), dual-in-line (DIL), dual-in-line with surface mount technology DIL-SMT, quad-flat-package (QFP), pin grid array (PGA) and ball grid array (BGA) and small outline packages. Other derivatives are for instance: plastic ball grid array (PBGA), ceramic ball grid array (CBGA), tape ball grid array (TBGA), super ball grid array (SBGA), micro ball grid array BGA® and leadframe packages or modules. A description of several standard packaging architectures can be found on the websites of several package manufacturers, e.g.: www.amkor.com (see also L. Halbo, P. Ohlckers, Electronic Components, Packaging and Production, ISBN: 82-992193-2-9).
In PCT/EP02/12427 (filed as well by the applicant, but not published when this current application was filed), attempts have been made in order to incorporate a miniature antenna to a package together with a semiconductor die.
Although this arrangement is suitable for certain applications it involves some disadvantages. More components in the package leads to a bigger size of the system. Another reason not to have a fully integrated solution is that some manufacturers incorporate their own processors onto the printed circuit board (PCB) and prefer to incorporate a package or module antenna rather than a fully integrated package. Moreover, having a circuit in the same package or module as the die itself, can increase the amount of heat to be dissipated and might lead to an increase of temperature of the whole system causing a malfunction of the die. Besides, interference between the antenna and the die might occur. This could lead to a decrease in the performance of the system.
In the last few years, several improvements in packaging technology have appeared mainly due to the development of Multichip Module (MCM) applications (see, for instance, N. Sherwani, Q. Yu, S. Badida, Introduction to Multi Chip Modules, John Wiley & Sons, 1995). Those consist of an integrated circuit package that typically contains several chips (i.e., several semiconductor dies) and discrete miniature components (biasing capacitors, resistors, inductors). Depending on the materials and manufacturing technologies, MCM packages are classified in three main categories: laminated (MCM-L), ceramic (MCM-C) and deposited (MCM-D). Some combinations thereof are possible as well, such as e.g. MCM-L/D and other derivations such as Matsushita ALIVH. These MCM packaging techniques cover a wide range of materials for the substrate (for instance E-glass/epoxy, E-glass/polyimide, woven Kevlar/epoxy, s-glass/cyanate ester, quartz/polymide, thermount/HiTa epoxy, thermount/polyimide, thermount/cyanate ester, PTFE, RT-Duroid 5880, Rogers RO3000® and RO4000®, polyiolefin, alumina, sapphire, quartz glass, Corning glass, beryllium oxide and even intrinsic GaAs and silicon) and manufacturing processes (thick film, thin film, silicon thin film, polymer thin film, LTCC, HTCC).